MLA
Battle, Cullen A. Letter from Cullen A. Battle (Petersburg, Virginia) to Mr. R. A. Sands. General Battle, from Alabama, Led a Brigade in Virginia - February 17, 1896. 1896. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 8, Folder 5. https://digital.library.emory.edu/purl/139x0k6f70-cor.
APA, 6th edition
Battle, C. A. (1896). Letter from Cullen A. Battle (Petersburg, Virginia) to Mr. R. A. Sands. General Battle, from Alabama, led a brigade in Virginia - February 17, 1896 (Box 8, Folder 5) [Letters (correspondence)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/139x0k6f70-cor.
Chicago
Battle, Cullen A. “Letter from Cullen A. Battle (Petersburg, Virginia) to Mr. R. A. Sands. General Battle, from Alabama, Led a Brigade in Virginia - February 17, 1896.” Letters (correspondence). Civil War Collection, 1896. Box 8, Folder 5. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/139x0k6f70-cor.